1. Field of the Invention
The present invention relates to a vacuum pump, and more particularly, to a vacuum pump having a fluid pump, and an exhaust system.
2. Description of the Related Art
A process chamber for manufacturing a semiconductor device or a flat panel display, for example, uses various chemicals such as a process gas. By-products and residual gases generated in the process chamber may be transmitted to a scrubber using a gas discharge apparatus such as a vacuum pump. The scrubber cleans and separates the by-products and the residual gases before discharging them.
The vacuum pump includes a stator and a rotor. The stator includes a suction port and a discharge port. The rotor is disposed in a pump chamber of the stator. Depending on the shape of the rotor, the vacuum pump may be classified as a roots type, a screw type, or a claw type pump.
FIG. 1 is a partial perspective view of a conventional roots pump that includes a rotary shaft 1, a pair of lobes 12, and a first diaphragm 15. The lobes 12 and the rotary shaft 11 constitute a rotor 13. A second diaphragm (not shown) may be disposed opposite to the first diaphragm 15, on top of the rotor 13, for example. A cylinder wall (not shown) may be disposed to surround a pump chamber 17 between the first diaphragm 15 and the second diaphragm so that the rotor 13 is disposed in the pump chamber 17. The cylinder wall includes a suction port and a discharge port. The cylinder wall, the first diaphragm 15, and the second diaphragm constitute the stator.
The rotary shaft 11 passes through the first diaphragm 15 and the second diaphragm. The rotary shaft 11 includes the pair of lobes 12 attached opposite to each other. Two rotors 13 may be disposed in the pump chamber 17 and mesh with each other.
As the rotors 13 rotate they suck a gas from the suction port into the pump chamber 17, and discharge the sucked gas through the discharge port. The suction port may be connected to a process chamber, and the discharge port may be connected to a scrubber. In summary, by-products are sucked from the process chamber into the pump chamber 17 through the suction port formed in the cylinder wall, and discharged from the pump chamber 17 to the scrubber through the discharge port.
Problems may arise if, while passing through the pump chamber 17, the by-products solidify to generate by-product masses 19. The by-product masses 19 may stick to surfaces in the pump chamber 17. For example, the by-product masses 19 stuck between the lobes 12 and the first diaphragm 15 or the second diaphragm may interfere with the rotation of the rotors 13. Eventually, the by-product masses 19 may cause a malfunction of the roots pump, thus requiring earlier maintenance.
Heating the stator is one method of reducing problems caused by sticky by-product masses 19. This method requires a stator formed of a material having a high thermal transfer efficiency. The method also requires an additional apparatus, and energy consumption, for heating the stator.
Meanwhile, another method of removing by-products and lengthening the maintenance cycle of a pump is disclosed in U.S. Pat. No. 5,173,041, entitled “Multistage vacuum pump with interstage solid material collector and cooling coils”, issued to Niimura, et al. According to Niimura, et al., a serial multistage roots pump is provided. A solid material collector having a cooling device is mounted at one side of the roots pump.
A method for removing by-product masses 19 without adding complexity to the manufacturing apparatus or increasing the required energy consumption is desired.